U.S. Pat. No. 3,380,646 discloses a container of thermally weldable, plastic material and a method of producing the container by welding together multiple strips or sheets of plastic material to form a container having a welded closed, bottom part of the container. An open top of the container is collapsed and flattened to provide a pinch closed top.
U.S. Pat. No. 5,048,692 discloses a bag folded one or more times to form a primary closure. A flap seal extends across the folded configuration. A string underneath the flap seal is used to tear open the flap seal and permit the bag to unfold. A zipper closure provides a secondary enclosure.
US 2007/0292053 A1 discloses a bag of paper material and a paper tape coated with a hot melt adhesive, wherein the tape is folded to adhere the hot melt adhesive against a front panel of the paper bag to provide a glued paper-to-paper section. The tape substitutes for a stepped end of a multi-wall paper bag. The stepped end provides a sealing flap coated with hot melt adhesive, wherein the sealing flap can be folded over and sealed to the front panel of the paper bag.
The hot melt adhesive is reactivated by a stream of hot air coming from a hot air sealer equipment. The equipment is designed to blow hot air only on the 1.5 inch width of pre-applied adhesive to render the adhesive to a heat activated adhesive state. Typical heat settings on a hot air sealer equipment for multi-wall paper bags often exceed 204.44° C. (400° F.). However, woven polypropylene bags will deform at approximately 148.89° C. (300° F.). A need exists to modify the equipment to seal woven polymeric bags at a reduced heat activation temperature. During the development of a pinch bottom closure for woven polymeric bags, it became clear that hot air sealer equipment that typically seal multi-wall paper bags needed to be modified.